docs: add docs, test for audio, video elements

[mohanraj-r]

Minor changes to doc, addition of tests as followup to #39

Documentation 📝

• add note about testing audio, video elements with Jest
• add references to sa11y blog post, a11y trailhead, SLDS
• remove unicode caution char ⚠️ from headings for TOC links to work

Chores 🧹

• test(integration): add jest, wdio tests for visual a11y issues (color contrast, audio/video elements)
• test: remove lint:version command from being run automatically until build: improve versioning workflow #40 is fixed
• build: add cmd to display info about changed files on the pkgs
• build: rename update dependencies cmd and include clean install as part of it
• bump versions of dev dependencies
• bump versions of following pkgs

@sa11y/test-utils        v0.2.2-beta.0 packages/test-utils       
@sa11y/test-integration  v0.1.4-beta.0 packages/test-integration
@sa11y/wdio              v0.1.1-alpha.1 packages/wdio
@sa11y/jest              v0.1.4-beta.1 packages/jest

[codecov]

Codecov Report

Merging #41 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #41   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           14        14           
  Lines          115       120    +5     
  Branches        10        10           
=========================================
+ Hits           115       120    +5     

Impacted Files	Coverage Δ
packages/test-utils/src/index.ts	100.00% <100.00%> (ø)
packages/test-utils/src/test-data.ts	100.00% <100.00%> (ø)